1. Field of the Invention
The present invention relates to novel amino acid derivatives and antihypertensive drugs containing them. The present invention also relates to methods of preparing these derivatives.
2. Detailed Description of the Invention
The present inventors have succeeded in the synthesis of novel amino acid derivatives represented by the general formula: ##STR2## Moreover, the present inventors have found that these derivatives, having an antihypertensive activity, are useful as antihypertensive drugs and intermediates for their production, and, based on this finding, have completed the present invention.
R.sub.1 and R.sub.2 in the foregoing formula, being the same or different from each other, each individually represents hydroxyl, alkyloxy, aryloxy, aralkyloxy, alkyl, aryl, or aralkyl.
The alkyloxy is lower alkyloxy having 1.about.5 carbon atoms such as methoxy, ethoxy, n-propyloxy, n-butyloxy, and n-pentyloxy.
The aryloxy is the one having 6.about.12 carbon atoms such as phenoxy, naphthyloxy, and p-tolyloxy.
The aralkyloxy is the one having 6.about.12 carbon atoms such as benzyloxy, phenetyloxy, phenylpropyloxy, and hydroxybenzyloxy.
The alkyl is a lower alkyl having 1.about.5 carbon atoms such as methyl, ethyl, n-propyl, n-butyl and n-pentyl.
The aryl is the one having 6.about.12 carbon atoms such as phenyl and p-tolyl.
The aralkyl is the one having 6.about.12 carbon atoms such as benzyl, phenethyl, and phenylpropyl.
R.sub.3, R.sub.5, R.sub.8, and R.sub.11 at least two of which are the same or all of which are different from one another, each individually represents hydrogen atom, or alkyl: for example, the one having 1.about.5 carbon atoms such as methyl, ethyl, n-propyl, n-butyl, and n-pentyl. That is to say, all of R.sub.3, R.sub.5, R.sub.8, and R.sub.11 may each individually represent hydrogen atom or methyl, or R.sub.3 and R.sub.5 may each individually represent hydrogen atom, and R.sub.8 and R.sub.11 may individually represents methyl; all of them may be different from one another: for example, R.sub.3 represents hydrogen atom, R.sub.5 represents methyl, R.sub.8 represents ethyl, and R.sub.11 represents isopropyl.
R.sub.4, R.sub.7, and R.sub.10 at least two of which are the same or all of which are different from one another, each individually represents hydrogen atom, or substituted or unsubstituted alkyl, aryl, or aralkyl.
The alkyl represents a lower alkyl having 1.about.5 carbon atoms such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, and n-pentyl.
The aryl represents the one having 6.about.12 carbon atoms such as phenyl, p-tolyl, and naphthyl.
The aralkyl represents the one having 6.about.12 carbon atoms such as benzyl and naphthylmethyl.
Substituent groups in the foregoing substituted groups may include, for example, hydroxyl, carboxyl, carbamoyl, amino guanidino, imidazolyl, indolyl mercapto, and lower alkylthio.
R.sub.6 and R.sub.9, being the same or different from each other, each individually represents hydrogen, alkyl, aryl, or aralkyl. The alkyl, the aryl, and the aralkyl, being, for example, the foregoing ones, may further include alicyclic compounds such as cyclopropyl, cyclopentyl, and cyclohexyl; and aromatic ring-condensed alicyclic compounds such as 2-indanyl and 1-indanyl.
R.sub.12 represents hydroxyl, alkyloxy, aryloxy, aralkyloxy, amino, mono- or di-alkyl-, aryl-, or aralkylamino. The alkyloxy, the aryloxy, the aralkyloxy, the alkyl, the aryl, and the aralkyl may each individually include, for example, those cited above as examples of R.sub.1 and R.sub.2.
R.sub.6 and R.sub.7, combined together, may form an alkylene bridge having 2.about.4 carbon atoms, and alkylene bridge having 2.about.3 carbon atoms and 1 sulfur atom, an alkylene bridge having 3.about.4 carbon atoms which contains a double bond, or substituted ones of these bridges; R.sub.9 and R.sub.10, combined together, may form the same alkylene bridges.
Examples of substituents on the foregoing bridges include hydroxyl, lower alkoxy, lower alkyl, oxo(o.dbd.), amino, condensed allyl, a condensed aromatic ring, and a condensed alicyclic ring.
Structures formed by such alkylene bridges may be, for example, the following ones: ##STR3##
Amino acids constituting the amino acid derivatives of the present invention may be either the L-isomer or the D-isomer.
The amino acid derivatives of the present invention may be in the form of a salt, such as a metal salt, as for example, sodium, potassium, lithium, and calcium salts or a salt with an organic base. As the organic base, there can be adopted amines such as ammonia (ammonium salt), dicyclohexylamine, and N-methyl-D-glucamine; and basic amino acids such as lysine and arginine.
When the amino acid derivatives are to be included in the antihypertensive drugs of the present invention, they need to be in a form of a pharmaceutically acceptable salt.
The amino acid derivatives of the present invention are tripeptide derivatives of which the terminal amino group is combined with a phosphorus compound (P), being represented by the formula: P--X--Y--Z (X, Y, and Z each represents an amino acid residue).
The amino acid corresponding to X typically includes alanine, leucine, isoleucine, glycine, phenylalanine, arginine, glutamic acid, glutamin, lysine, valine, ornithine, methionine, serine, and threonine; the amino acid corresponding to Y typically includes proline, hydroxyproline, glycine, N-substituted glycine, and thioproline; the amino acid corresponding to Z typically includes proline, hydroxyproline, glycine, alanine, serine, aspartic acid, arginine, tyrosine, phenylalanine, valine, leucine, isoleucine, threonine, methionine, glutamic acid, glutamine, lysine, cystine, tryptophan, and histidine.
When the tripeptide derivative has functional groups, the functional groups may be protected by protecting groups ordinarily used in synthetic chemistry of peptides; the protected derivatives are also encompassed by the amino acid derivatives of the present invention.
Examples of methods for preparation are as follows:
Method 1: ##STR4## wherein R.sub.1.about.12 each individually represents the same as defined above.
The desired compound can be prepared by causing a phosphoridate [III] such as phosphochloridatediester and phosphochloridatemonoester to react with, for example, a hydrochloride derivative of ester or amide of the tripeptide derivative [II] in an inert solvent such as methylene chloride in the presence of a base such as triethylamine to transform the N-terminal of an the tripeptide derivative into a phosphorus derivative, followed, if necessary, by selectively removing protecting groups by means of hydrolysis with an alkali, catalytic hydrogenation, or the like.
On the other hand, the desired compound can also be prepared by directly condensing a phosphoridate [III] with a free compound of the tripeptide derivative [II].
Method 2: ##STR5## wherein R.sub.1.about.12 each individually represents the same as defined above.
The desired compound can be prepared by subjecting a phosphorus derivative of a dipeptide [IV] and an amino acid derivative [V] such as a hydrochloride of ester or amide to a condensation reaction in an inert solvent such as dimethylformamide (DMF) with the use of a condensing agent such as N,N'-dimethylaminopropylethylcarbodiimide (WSC) and 1-hydroxybenzotriazole (HOBt) to obtain a phosphorus derivative of the tripeptide [I], followed, if necessary, by selectively removing protecting groups by means of hydrolysis with an alkali or catalytic hydrogenation.
Method 3: ##STR6## wherein R.sub.1.about.12 each individually represents the same as defined above.
The desired compound can be obtained by subjecting a phosphorus derivative of an amino acid [VI] and a dipeptide derivative [VII] such as a hydrochloride of ester or amide to a condensation reaction in an inert solvent such as dimethylformamide with the use of a peptide condensating agent used in synthetic chemistry of peptides, such as WSC and HOBt, to obtain a phosphorus derivative of a tripeptide, followed, if necessary, by selectively removing protecting groups by means of hydrolysis with an alkali or catalytic hydrogenation.
The methods will be illustrated with more specific examples below.
A substituted phosphoryl derivative can be prepared by preparing a peptide derivative represented by the general formula: ##STR7## wherein Z represents the same as defined above, followed by causing the peptide derivative to react with a substituted phosphoryl halogenide such as diethyl- or dibenzylphosphoryl chloride. The substituted phosphoryl derivative, for example, dibenzylphosphoryl chloride, can be converted into a phosphoryl derivative by subjecting it to hydrogenation using palladium carbon as catalyst.
The foregoing tripeptide, an intermediate for the derivatives of the present invention, can be prepared by causing an alanine having a protected amino group to react with a proline having a protected carboxyl group to prepare alanylproline, removing the protecting groups of the alanylproline, and causing the resulting product to react with the Z component, an amino acid having a protected amino group, followed, if necessary, by removing the protecting group.
On the other hand, the tripeptide can also be prepared by preparing dibenzylphosphorylalanylproline, followed by causing the product to react with the foregoing selected amino acid ester according to the method of Japanese patent first publication No. 104863/1981.
An alanylproline derivative of which the constituent proline residue has a hydroxyl group (hydroxyproline) can also be prepared in the same manner.
Those protecting groups for amino, imino, carboxyl, and hydroxyl groups, those methods for the protection, those methods for removal of the protecting groups, and those methods for amide-linking by condensation between amino and carboxyl groups which are all employed in the preparation of the derivatives of the present invention and intermediates therefore may be the ones ordinarily used in methods for peptide synthesis or generally or conventionally employed in the known literature, for example, Protein Chemistry, 1 Amino Acid.Peptide, e.g. pages 405.about.509 (1969), compiled by Shiro Akabori, Takeo Kaneko, and Kozo Narita, published by Kyoritsu Shuppan Co. An amide-linkage is advantageously formed from an amino acid by a condensation method in which an active ester of the amino acid having a protected amino group, such as p-nitrophenylester and N-hydroxysuccinimideester, is used for reaction. When a solvent is used in the reaction, DMF or water can be adopted as solvent. The reaction temperature may be a room temperature or so, but the reaction can also, as needed, be accelerated by heating.
The derivatives of the present invention are isolated from the reaction mixture by concentrating the reaction mixture to dryness, purifying the residue by means of column chromatography, followed by lyophilization of the product.
When the derivatives of the present invention are used, as an active ingredient, for an antihypertensive drug, there may be adopted their free forms, their nontoxic forms of salt, or their nontoxic forms having protecting groups. An amino acid constituting the derivatives for use as an antihypertensive drug of the present invention may be either the L-isomer or the D-isomer.
The amino acid derivatives of the present invention are useful as an antihypertensive drug for treating hypertensive mammals including humans. The derivatives can be used for lowering blood pressure by formulating them into a preparation such as tablets, capsules, and elixirs for oral administration and into an aspetic liquid preparation or an aseptic suspension preparation for parenteral administration. The amino acid derivatives of the present invention can be administered to a subject necessitating such treatment (animals and humans) in a dosage range of 0.2.about.500 mg per subject generally several times a day, that is, in a total daily dosage of 1.about.2000 mg. The dosage varies according to the seriousness of disease, the body weight of subjects, and other factors acknowledged by those skilled in the art.
The amino acid derivatives of the present invention can also be administered together with diuretics or other antihypertensive drugs. Typically, these drugs are administered in a dosage combination of which one unit of daily dose is in the range from 1/3 times as large as a clinical dosage minimally recommended to a level maximally recommended singly for each entity of disease. These combinations are specially shown as follows: A kind of antihypertensive drugs of the present invention which is clinically effective in a daily dosage range of 15.about.200 mg can effectively be administered together with the following other antihypertensive drugs and diuretics in a daily dosage range of 3.about.200 mg: hydrochlorothiazide (15.about.200 mg), chlorothiazide (125.about.2000 mg), ethacrynic acid (15.about.200 mg), amiloride (5.about.20 mg), furosemide (5.about.80 mg), propranolol (20.about.480 mg), timolol (5.about.50 mg), methyldopa (65.about.2000 mg). The foregoing dosage ranges are adjusted on the basis of unit according to the necessity for the possible daily divided dosage. The dosage varies according to the seriousness of disease, the body weight of subject, and other factors acknowledged by those skilled in the art.
The foregoing typical combinations of drugs are formulated into pharmaceutical compositions stated below. About 0.2.about.500 mg of the derivatives of the present invention, pharmaceutically acceptable salt compounds, or mixtures of both are blended into unit dosage forms generally acknowledged or required for the pharmaceutical practice together with pharmaceutically acceptable vehicles, carriers, excipients, binders, antiseptics, stabilizers, flavorings, and so forth. The amount of each active substance in these compositions or preparations is adjusted in such a way as to give an appropriate dosage of the prescribed range.
Specific materials which can be incorporated into tablets, capsules, and so forth are as follows: A binder such as traganth, gum arabic, cornstarch, and gelatin; an excipient such as microcrystalline cellulose; a swelling agent such as cornstarch, pregelatinized starch, and arginic acid; a lubricant such as magnesium stearate; a sweetner such as sucrose, lactose, and saccharin; a flavoring such as peppermint, an oil from Gaultheria adenothrix Maxim, and cherry. When the unit dosage form of the preparation is a capsule, a liquid carrier such as fatty oil can further be incorporated in the foregoing type materials. Various other materials can be present as a coating material or in order to vary the physical form of unit dosage forms according to other methods. For example, tablets can be coated with shellac and/or sugar. Syrups or elixirs can contain active compounds, sucrose as a sweetner, methyl- and propylparaben as an antiseptic, a coloring matter, a flavoring such as cherry and an orange flavoring.
Aseptic compositions for injection can be formulated according to the usual practive for preparation of pharmaceutical dosage forms, in which practice an active substance is dissolved or suspended in a vehicle such as water for injection; natural vegetable oils such as sesame oil, palm oil, peanut oil, and cotton seed oil; and synthetic fat vehicle such as ethyl oleate. A buffer, an antiseptic, and an antioxidant can further be incorporated as occasion demands.